Modern conferencing systems facilitate communications among multiple participants over telephone lines, Internet protocol (IP) networks, and other data networks. In a typical conferencing session, a participant enters the conference by using an access number. During the conference a mixer receives audio streams from the participants, determines the N loudest speakers, mixes the audio streams from the loudest speakers and sends the mixed audio back to the participants. In a video conference, both audio and video streams are mixed and delivered to the conference participants. In some cases, both audio-only participants and audio/video participants may join in the meeting.
Integrating video into an audio-only conferencing system often requires a large investment in the development of video codec technology, hardware architecture, and the implementation of video features necessary to produce a competitive product. To avoid this investment, developers have attempted to integrate an existing (“off-the-shelf”) audio/video (A/V) multipoint control unit (MCU) with an existing audio-only product. Past approaches for accommodating such integration have typically involved hosting an audio conference on an audio bridge for audio-only participants and an A/V conference on the video MCU for the audio/video participants. The two conferences are then linked together by cascading the audio output of the audio conference as an input into audio/video conference, and vice versa. One problem with this approach, however, is that in-conference features are available for audio-only participants but not A/V participants. Furthermore, the audio quality as perceived by A/V users and audio-only users is different, which leads to customer dissatisfaction.